The present invention relates to a disk brake suitably used to apply braking force to a vehicle, for example.
A generally known disk brake includes a caliper having a bridge portion extending over the outer periphery of a disk. A cylinder bore is formed at one side of the bridge portion. An outer leg portion is formed at the other side of the bridge portion. The outer leg portion has at least a pair of claw portions. The disk brake further includes inner and outer friction pads extending in the circumferential direction of the disk at respective positions on both sides of the disk. The friction pads are adapted to be pressed against both sides of the disk by the caliper.
In this type of disk brake, when the brake is activated, a piston provided in the cylinder bore of the caliper is caused to slide toward the disk by a fluid pressure supplied externally so as to press the friction pads against both sides of the disk in cooperation with the claw portions of the outer leg portion, thereby applying braking force to the disk.
When the vehicle is braked by the disk brake, braking torque from the disk that is transmitted through the friction pads undesirably acts as a bending moment on the caliper. Accordingly, the inner friction pad has such a tendency that the surface pressure applied to the disk is relatively high at the entrance side in the rotational direction of the disk and relatively low at the exit side. Consequently, the inner friction pad is likely to wear non-uniformly at the entrance side.
Therefore, according to the conventional technique, the cylinder bore is decentered (i.e., the center axis is shifted) toward the exit side in the rotational direction of the disk with respect to the friction pads. Consequently, the surface pressure of the inner friction pad applied to the disk is reduced at the entrance side, and thus non-uniform wear of the friction pad is suppressed.
Incidentally, the disk brake according to the above-described conventional technique is arranged such that, among the cylinder bore, the bridge portion and the outer leg portion that constitute the caliper, the cylinder bore is decentered toward the exit side in the rotational direction of the disk with respect to the longitudinal center position of the friction pads.
However, the claw portions of the outer leg portion are formed such that the space therebetween is defined as a recess for machining the cylinder bore. Therefore, the recess is usually decentered toward the exit side in the rotational direction of the disk with respect to the friction pads in accordance with the amount that the cylinder bore has been decentered (i.e., decentration of the cylinder bore). As a result of decentering the recess of the outer leg portion toward the exit side in the rotational direction of the disk, the entrance-side claw portion as viewed in the rotational direction of the disk has a large wall thickness in the circumferential direction of the disk in comparison to the exit-side claw portion.
Consequently, when the brake is activated, there is a difference in rigidity between the claw portions. The rigidity difference may cause the claw portions pressing the outer friction pad in particular to differ in the surface pressure from each other. In such a case, the friction pad is worn non-uniformly, and it becomes likely that brake noise, judder and so forth will occur owing to the non-uniform wear of the friction pad.